Notably Polite Mariner


    5.0.2 • Public • Published


    DISCLAIMER: not my repo, just needed some extra features (maybe I'll push the changes sometime to the origin repo)

    Build Status Coverage Status

    The smallest, simplest and fastest JavaScript pixel-level image comparison library, originally created to compare screenshots in tests.

    Features accurate anti-aliased pixels detection and perceptual color difference metrics.

    Inspired by Resemble.js and Blink-diff. Unlike these libraries, pixelmatch is around 90 lines of code, has no dependencies, and works on raw arrays of image data, so it's blazing fast and can be used in any environment (Node or browsers).

    var numDiffPixels = pixelmatch(img1, img2, diff, 800, 600, {threshold: 0.1});

    Implements ideas from the following papers:

    Example output

    expected actual diff


    pixelmatch(img1, img2, output, width, height[, options])

    • img1, img2 — Image data of the images to compare (Buffer or Uint8Array). Note: image dimensions must be equal.
    • output — Image data to write the diff to, or null if don't need a diff image.
    • width, height — Width and height of the images. Note that all three images need to have the same dimensions.

    options is an object literal with the following properties:

    • threshold — Matching threshold, ranges from 0 to 1. Smaller values make the comparison more sensitive. 0.1 by default.
    • includeAA — If true, disables detecting and ignoring anti-aliased pixels. false by default.

    Compares two images, writes the output diff and returns the number of mismatched pixels.

    Command line

    Pixelmatch comes with a binary that works with PNG images:

    pixelmatch image1.png image2.png output.png 0.1

    Example usage


    var fs = require('fs'),
        PNG = require('pngjs').PNG,
        pixelmatch = require('pixelmatch');
    var img1 = fs.createReadStream('img1.png').pipe(new PNG()).on('parsed', doneReading),
        img2 = fs.createReadStream('img2.png').pipe(new PNG()).on('parsed', doneReading),
        filesRead = 0;
    function doneReading() {
        if (++filesRead < 2) return;
        var diff = new PNG({width: img1.width, height: img1.height});
        pixelmatch(,,, img1.width, img1.height, {threshold: 0.1});


    var img1 = img1Ctx.getImageData(0, 0, width, height),
        img2 = img2Ctx.getImageData(0, 0, width, height),
        diff = diffCtx.createImageData(width, height);
    pixelmatch(,,, width, height, {threshold: 0.1});
    diffCtx.putImageData(diff, 0, 0);


    Install with NPM:

    npm install pixelmatch

    To build a browser-compatible version, clone the repository locally, then run:

    npm install -g browserify
    browserify -s pixelmatch index.js > pixelmatch.js



    npm i @schornio/pixelmatch

    DownloadsWeekly Downloads






    Last publish


    • schornio